Emulsifiable Marine Lower Unit Gear Oil

ABSTRACT

A lubricant composition for lower unit gear drives in outboard and stern drive engines is disclosed. The lubricant composition comprises: (a) a highly sulfurized olefin; (b) an amine salt of a phosphorus compound; (c) a high molecular weight PIBSA-PAM dispersant; and (d) a copper corrosion inhibitor.

This Patent Application claims priority from Provisional Patent Application No. 60/871,213 filed Dec. 21, 2006.

FIELD OF THE INVENTION

The present invention relates to additive packages for lubricant compositions and related lubricant compositions; especially additive packages for lubricant compositions suitable for use in lower unit gear drives for outboard and stern drive engines.

BACKGROUND

Lower unit gear drives are used with boat outboard and stern drive engines and other similar marine applications. The lower unit gear drives transmit power from the marine engine to a propeller.

The current trend is to equip boats with more powerful engines and more compact gear drives. As a result, lower unit gear drives are being required to support increased loads. New lower unit gear drive lubricant compositions are required to maintain acceptable performance under the higher severity operating conditions.

Because lower unit gear drives are submerged in water while a boat is being operated, it is highly likely that some water will ingress into the gear drive lubricant. Consequently, effective lubricant compositions for lower unit gear drives must be able to compensate for the possible negative effects of the presence of water in the lubricant.

The present invention provides a new additive package for a lubricant composition to be used in a lower unit gear drive comprising: (a) a highly sulfurized olefin; (b) an amine salt of a phosphorus compound; (c) a high molecular weight polyisobutylene succinic anhydride amine (also referred to herein as “PIBSA-PAM”) dispersant; and (d) a copper corrosion inhibitor. The lubricant composition of the invention exhibits the required amount of extreme pressure performance, anti-wear performance, anti-corrosion performance, and anti-rust performance.

SUMMARY OF THE INVENTION

In a non-limiting embodiment, the present invention is a lubricant composition for lower unit gear drives in outboard and stern drive engines comprising: (a) a highly sulfurized olefin; (b) an amine salt of a phosphorus compound; (c) a high molecular weight PIBSA-PAM dispersant; and (d) a copper corrosion inhibitor.

DESCRIPTION OF THE INVENTION

Unless otherwise indicated, all numbers expressing quantities of ingredients, reaction conditions, dimensions, physical characteristics, processing parameters, and the like, used in the specification and claims are to be understood as being modified in all instances by the term “about”. Accordingly, unless indicated to the contrary, the numerical values set forth in the following specification and claims may vary depending upon the desired properties sought to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical value should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Moreover, all ranges disclosed herein are to be understood to encompass the beginning and ending range values and any and all sub ranges subsumed therein. For example, a stated range of “1 to 1.0” should be considered to include any and all sub ranges between (and inclusive of) the minimum value of 1 and the maximum value of 10; that is, all sub ranges beginning with a minimum value of 1 or more and ending with a maximum value of 10 or less, e.g., 5.5 to 10. Any mentioning of a U.S. patent or patent document or literature reference in the following description also incorporates by reference that document herein and is to be understood to be incorporated in its entirety.

The present invention is an additive package for a lubricant composition that can be used in a lower unit gear drive. According to the present inventions the additive package comprises; (a) a highly sulfurized olefin; (b) an amine salt of a phosphorus compound; (c) a high molecular weight PIBSA-PAM dispersant; and (d) a copper corrosion inhibitor.

The highly sulfurized olefin of the present invention can provide extreme pressure performance. In a non-limiting embodiment of the invention, the highly sulfurized olefin is sulfurized isobutylene.

The amine salt of a phosphorus compound of the present invention can provide anti-wear performance. In a non-limiting embodiment, the amine salt of a phosphorus compound is an amine salt of a phosphoric acid ester, for example, a 2-ethylhexyl phosphate ester amine salt. In a non-limiting embodiment, the amine is a C₁₂ to C₁₄ t-alkyl primary amine.

In another non-limiting embodiment of the invention, the amine salt of a phosphoric acid ester has a low amine/phosphorus molar ratio. For example, the 2-ethylhexyl phosphate ester is reacted with an amine to form a partially neutralized salt having a molar ratio of 0.5 or less moles of amine per mole of phosphorus.

In yet another non-limiting embodiment, the amine salt of a phosphorus compound is an amine comprising the reaction product of methyl isobutyl carbinol dithiophosphoric acid with propylene oxide. The resultant alcohol is further reacted with phosphorus pentoxide and then partially neutralized with a C₁₂ to C₁₄ t-alkyl primary amine.

In another non-limiting embodiment of the invention, the ratio of the highly sulfurized olefin to the amine salt of a phosphorus compound is 15:1 sulfur-to-phosphorus mass ratio to 40:1 sulfur-to-phosphorus mass ratio, or 20:1 to 30:1 sulfur-to-phosphorus mass ratio.

The high molecular weight PIBSA-PAM dispersant of the present invention can act as a water emulsifier. In a non-limiting embodiment, the PIBSA-PAM has a molecular weight of 2000 or higher.

In another non-limiting embodiment, the high molecular weight PIBSA-PAM dispersant is non-borated. In the present invention, a non-borated PIBSA-PAM dispersant is more desirable than a borated PIBSA-PAM dispersant. By including a non-borated PIBSA-PAM dispersant in the composition, the potential for deposition of boron-containing species is reduced in the event water comes in contact with the composition.

The copper corrosion inhibitor of the present invention can comprise a tolyltriazole compound or a thiadiazole compound.

In a non-limiting embodiment, the additive package of the present invention further comprises a fragrant component (i.e., a component added to affect the smell of the additive package and related lubricant compositions that contain the additive package). An example of a suitable fragrant component is Fragrance OM 69B which is commercially available from Quest International.

The present invention also encompasses a lubricant composition comprising additive package described above. As is well known in the art, a lubricant composition can be formed by adding conventional base oils, typically Group I base oils, to the described additive package.

In a non-limiting embodiment of the lubricant composition of the present invention, the high molecular weight PIBSA-PAM dispersant contributes nitrogen to the lubricant composition in an amount ranging from 10 ppm to 500 ppm.

According to the present invention, the lubricant composition can comprise the following optional components which are well known in the art: rust inhibitors; non-silicone, antifoam agents and tackifiers.

Suitable rust inhibitors are well known in the art and include, but are not limited to, 2-ethylhexyl amine commercially available from Celanese Ltd. as 2-Ethylhexylamine and a tallow amine commercially available from Goldschmidt Chemical as Adogen 170.

Suitable non-silicone, antifoam agents are well known in the art and include, but are not limited to, non-silicone, antifoam agents commercially available from Cytec Surface Specialties as PC 1644

Suitable tackifiers are well known in the art and include, but are not limited to, tackifiers which are commercially available from Infineum USA LP as Paratac.

In a non-limiting embodiment of the present invention, the lubricant composition comprises essentially no heavy metals, such as antimony. For example, a lubricant according to the present invention can contain less than or equal to 0.25 weight percent of antimony, for example 0.15 to 0.25 weight percent of antimony. Many commercially available lubricant compositions contain antimony to provide superior extreme pressure performance. However, tightening regulatory constraints may force these additive packages containing heavy metals out of the lower unit gear oil market.

As discussed above, the lubricant composition of the present invention is typically used in a lower unit gear drive which will be submerged in water while it is being operated. Consequently, it is highly likely that some water ingress will occur, for example, through the lower unit's propeller shaft seals. This water will mix with the lubricant composition in the gear drive. The exact amount of water in the lubricant composition depends on such factors as the rate of water ingress into the lubricant composition, oil drain intervals, etc. Under typical operating conditions, the amount of water which can accumulate in the lubricant composition could range from 2 to 10 volume %.

If water mixes with the lubricant composition and is not emulsified into the lubricant composition but rather remains a separate phase from the composition, the lubrication of the various components of the lower unit gear drive system would be shared by the lubricant composition phase and the free water phase. This would be very detrimental as the free water phase would not provide any lubrication and could corrode any metal parts which are part of the gear drive system. Consequently, no demulsifier such as, but not limited to, those commercially available under the Pluronic brand from BASF [Germany] is added to the lubricant composition of the present invention.

Due to the chemical structure of the high molecular weight PIBSA-PAM dispersant and its amount in the lubricant composition, any water that mixes with the lubricant composition is emulsified resulting in a single phase of emulsified water in the lubricant composition. The polar attraction between water and the non-borated, high molecular weight PIBSA-PAM dispersant causes the emulsification.

EXAMPLES

The following non-limiting examples illustrate the present invention. Examples 1 and 2 are additive packages according to the present invention. Example 1 was prepared by blending (a) a highly sulfurized olefin commercially available from ExxonMobil Chemical Company as Mobilad C170 which is 53.444 mass percent of the additive package; (b) an amine phosphate comprising the reaction product of methyl isobutyl carbinol dithiophosphoric acid with propylene oxide which was further reacted with phosphorus pentoxide and then partially neutralized with a C₁₂ to C₁₄ t-alkyl primary amine as the amine salt of a phosphorus compound which is 12.222 mass percent of the additive package; (c) a non-borated, high molecular weight PIBSA-PAM dispersant commercially available from Infineum USA LP as Infineum C9280 which is 16.667 mass percent of the additive package; and (d) a thiadiazole copper corrosion inhibitor commercially available from Afton as HiTEC 4315 which is 3.333 mass percent of the additive package.

The following optional materials were added to form the additive package of Example 1: two rust inhibitors-2-ethylhexyl amine commercially available from Celanese Ltd. as 2-Ethylhexylamine and a tallow amine commercially available from Goldschmidt Chemical as Adogen 170 which are collectively 0.444 mass percent of the additive package, a non-silicone, antifoam agent commercially available from Cytec Surface Specialties as PC 1644 which is 0.444 mass percent of the additive package, SN150 Group I base oil as a diluent commercially available from ExxonMobil as ExxonMobil Core 150 which is 13.400 mass percent of the additive package and a fragrance commercially available from Quest International as Fragrance OM 69B which is 0.044 mass percent of the additive package. The blending was conducted using standard procedures and techniques.

Example 2 was prepared by blending (a) a highly sulfurized olefin commercially available from ExxonMobil Chemical Company as Mobilad C170 which is 56.667 mass percent of the additive package; (b) an amine salt of a phosphorus compound formed by reacting 2-ethylhexyl phosphate ester commercially available from P-4 Technology as 2EHAPO4 with a C₁₂ to C₁₄ t-alkyl primary amine commercially available by Rohm & Haas as Primene 81R which is 10.622 mass percent of the additive package; (c) a non-borated, high molecular weight PIBSA-PAM dispersant commercially available from Infineum USA LP as Infineum C9268 which is 16.667 mass percent of the additive package; and (d) a tolyltriazole (10% solution) copper corrosion inhibitor which is 6.667 mass percent of the additive package.

The following optional materials were added to form the additive package of Example 2: 2-ethylhexyl amine rust inhibitor commercially available from Celanese Ltd. as 2-Ethylhexylamine which is 0.222 mass percent of the additive package, a non-silicone, antifoam agent commercially available from Cytec Surface Specialties as PC 1644 which is 0.444 mass percent of the additive package, SN150 Group I base oil commercially available from ExxonMobil as ExxonMobil Core 150 as a diluent which is 8.667 mass percent of the additive package and a fragrance commercially available from Quest International as Fragrance OM 69B which is 0.044 mass percent of the additive package. The blending was conducted using standard procedures and techniques.

An 80W-90 viscosity grade lubricant composition (according to the SAE J306 Automotive Gear Lubricant Viscosity Classification) was formed by adding the following to the additive described above in Example 1 which is 4.5 mass percent of the composition: a pour point depressant commercially available from Infineum USA LP as Infineum V385 which is 1.5 mass percent of the composition, a tackifier which is commercially available from Infineum USA LP as Paratac and is 0.1 mass percent of the composition, a Group I base oil commercially available from CITGO as CITGO 325N which is 53.4 mass percent of the composition and a Group I base oil commercially available from CITGO as CITGO Brightstock which is 40.5 mass percent of the composition. The lubricant composition had an ASTM D445 kinematic viscosity at 100° C. (KV100) 14.3 cSt and an ASTM D2983 Brookfield viscosity at −26° C.=122,000 cP.

The formulated lubricant composition was subjected to the ASTM D3233 Falex Pin-and-Vec Test for anti-wear and extreme pressure performance. In a first run of the test, the lubricant composition was tested and had a failure load result of greater than 4500 lbs. In a second run of the test, a lubricant composition with 2% by volume added water was tested and had a failure load result of greater than 4500 lbs. In a third run of the test, a lubricant composition with 5% by volume added water was tested and had a failure load result of 4500 lbs. in a fourth run of the test, a lubricant composition with 10% by volume added water was tested and had a excellent failure load result of 4500 lbs.

Based on the results of these tests, a lubricant composition according to the present invention that has up to 10% water by volume exhibits excellent anti-wear and extreme pressure performance. 

1. An additive package for lower unit gear drives in outboard and stern drive engines comprising: (a) a highly sulfurized olefin; (b) an amine salt of a phosphorus compound; (c) a high molecular weight PIBSA-PAM dispersant having a molecular weight of 2000 or higher; and (d) a copper corrosion inhibitor.
 2. The additive package according to claim 1 wherein the highly sulfurized olefin comprises sulfurized isobutylene.
 3. The additive package according to claim 1 wherein the amine salt of a phosphorous compound comprises a C₁₂ to C₁₄ t-alkyl primary amine.
 4. The additive package according to claim 1 wherein the amine salt of a phosphorus compound is an amine comprising the reaction product of methyl isobutyl carbinol dithiophosphoric acid with propylene oxide.
 5. The additive package according to claim 1 wherein the amine salt of a phosphorus compound comprises an amine salt of a phosphoric acid ester.
 6. The additive package according to claim 5 wherein the amine salt of the phosphoric acid ester has a low amine/phosphorus molar ratio.
 7. The additive package according to claim 1 wherein the ratio of the highly sulfurized olefin to the amine salt of a phosphorus compound is 15:1.
 8. The additive package according to claim 1 wherein the high molecular weight PIBSA-PAM dispersant is non-borated.
 9. The additive package according to claim 1 wherein the copper corrosion inhibitor comprises a tolyltriazole compound.
 10. The additive package according to claim 1 wherein the copper corrosion inhibitor comprises a thiadiazole compound.
 11. A lubricant composition for lower unit gear drives in outboard and stern drive engines comprising: (a) a highly sulfurized olefin; (b) an amine salt of a phosphorus compound; (c) a high molecular weight PIBSA-PAM dispersant; and (d) a copper corrosion inhibitor, wherein the lubricant composition is in the lower unit gear drives.
 12. The lubricant composition according to claim 11 wherein nitrogen from the high molecular weight PIBSA-PAM dispersant is present in an amount ranging from 10 ppm to 500 ppm.
 13. The lubricant composition according to the claim 1 comprising essentially no heavy metals.
 14. The lubricant composition according to claim 13 comprising less than or equal to 0.25 weight percent of antimony. 